ABSTRACT: The factors influencing the European Commission's decisions under the 2004 Merger Regulation are assessed on a sample of 50 cases. Probit analysis results in the finding that the probability of nonclearance in phase I of the procedure is significantly affected by the estimated market share increase due to the proposed merger, the contestability of the market, and the presence of barriers to entry. Furthermore, there is some evidence that the Commission's decisions are biased against market leaders involved in proposed mergers.